Mechanical properties of the novel L1₂-Ir₃Z ultra-high temperature alloys (Z =Ti, V, Zr, Nb, Hf and Ta)

Ir₃Z (Z = Ti, V, Zr, Nb, Hf and Ta) ultra-high temperature alloys, well known as their high melting point and excellent mechanical properties, are promising candidates for high temperature structural materials beyond nickel-based materials. Nevertheless, knowledge of their mechanical properties and the mechanism of tensile/shear deformation still remains poor. In this work, the fundamental mechanical properties and mechanical behavior under different tensile/shear loading directions of Ir₃Z alloys were studied using DFT calculations. All Ir₃Z alloys have very high mechanical moduli (404.7–561.3 GPa for Young's modulus). For both mechanical and tensile/shear strength, Ir₃V, Ir₃Nb and Ir₃Ta are distinctly superior to Ir₃Ti, Ir₃Zr and Ir₃Hf, in which Ir₃V shows the most outstanding performance. Furthermore, these alloys exhibit similar tensile/shear stress-strain relationship and all of them show anisotropic mechanical behavior under strain, i.e., [100] direction shows the strongest resistance to tensile stress and (111)/[1(_)10] turns out to be the most likely slip system. Meanwhile, the results of average charge density as well as the density of states diagram suggest that the degree of interatomic bonding mainly determines the ideal strength of different structure and tensile/shear direction of Ir₃Z alloys.